A person (usually a man) who counts all of the girls (or guys, if a woman) he is able to get with in a certain period of time. It could be within his entire life time or it could even be within a week.
Person A: In the past month I've hooked up with six girls and I've had sex with two of them.
Person B: Man, you're a number runner.
Person B: Man, you're a number runner.
by Number Runner December 26, 2009